(1) Field of the Invention
The present invention relates to an improvement of a printing apparatus which conducts printing by giving impact to a printing medium set on the platen with a print head and then ejects the printing medium from an exhaust port.
An impact printer such as a wire dot-matrix printer is already used widely because of its low-cost characteristics and duplicating function.
However, such impact printer generates impact noise during the printing operation and such impact noise is considered as a problem of this printer. Recently, the printing apparatus has often been installed in offices as an output device of a personal computer, etc. and therefore it has also been intensively requested to reduce the level of printing noise. Particularly, the front end noise of the printer results in a serious problem because an operator usually stays in front of the printer.
It has of course been discussed how to suppress the impact noise generated during printing operation by improvement of the print head itself, but the method to suppress impact noise is naturally has a limitation. Therefore, it is also necessary, from the structural view point of apparatus, to realize reduction of impact noise.
Meanwhile, it is also impressively expected that a printing apparatus accepts a variety of printing media, such as papers in different thickness and rigidity, for example, an ordinary paper and paper-stapled sheet [a plurality of papers are gathered and bound with a pressing force thereto].
(2) Description of the Prior Art
FIGS. 1(a), 1(b) respectively show conventional printers. In the printer shown in FIG. 1(a), an aperture 3a designed as the exhaust port for papers is provided above the platen 2 and a print head is also provided at the left side of platen 2.
The print head 1 makes spacing movement along the platen 2 to execute the printing on a cut sheet inserted from the guide 6 or a continuous sheet transferred by a tractor 5. A bail roller 4 for pressing the paper is provided between the print head 1 and a top cover 3 provided at the upper part of print head 1. This bail roller 4 moves in the direction indicated in the figure to cause the paper running toward the direction of arrow mark A to move toward the direction of arrow mark B and then exhaust the paper from the aperture 3a.
A sound insulation material 7 is provided at a part other than the neighborhood of bail roller 4 of the top cover 3.
In the printer having such structure, the impact noise of print head is suppressed by the sound insulation material 7 of the top cover 3 as much as not leaking to the front side of printer.
On the other hand, in the horizontal type printer as shown in FIG. 1(b), an aperture 3 which is designed as the exhaust port of paper is provided in the left side of platen 2 and the print head 1 is provided at the lower part of platen 2. The cut sheet (SP) from the guide 6 or the continuous sheet (LP) transferred by the tractor 5 is transferred almost horizontally and exhausted forward from the aperture 3a provided at the front side of apparatus after completing the printing by the print head.
In the printer as shown in FIG. 1(a), since the aperture 3a is provided at the upper part of platen 2, the printing result on the paper exhausted therefrom can be checked easily. However, the print head 1 is provided at the lower part of the top cover 3 to result in the problem that it becomes near the cover aperture 3a, noise of print head 1 leaks easily therefrom and resultant forward noise becomes high level.
Moreover, since a movable bail roller 4 is provided above the print head 1, the sound insulating material 7 is not provided to this part of the top cover 3. Accordingly, sufficient sound insulation effect by the top cover 3 cannot be obtained in this case, resulting in a problem that the forward noise level cannot be lowered.
In the case of a printer shown in FIG. 1(b), the aperture 3a is provided at the front area of apparatus and the print paper is exhausted with the printing (front) side placed rear side. Therefore, it is difficult to check the printing result. In addition, the forward noise level is high because the impact noise of print head 1 is released forward in direct.
From the point of view of a kind of paper to be used, thickness and rigidity are different from the paper to paper in accordance with a kind of paper. Therefore, a printer as shown in FIG. 1(a), FIG. 1(b) having the one exhaust path and the one exhaust direction cannot realize smooth transfer of paper for every kind of paper without occurrence of sheet jamming and improper line feeding.